Bash Script – Arithmetic Operators

In this article, we will see arithmetic operators in bash script. Arithmetic operators is used to perform arithmetic operations.

Bash script supports 11 arithmetic operators. All the operators with their uses is given below:

Operator	Name	Use	Example
+	Addition	It adds two operands	result= a+b
–	Subtraction	It subtract second operand from first one	result= a-b
*	Multiplication	Multiply two operands	result= a*b
/	Division	Return the quotient after diving first operand from second operands	16/3 result = 5
%	Modulo	Return remainder after dividing first operand from second operand	16/ 3 result = 1
+=	Increment by constant	Increment value of first operand with given constant value	x= 13 x+=3 result = 16
-=	Decrement by constant	Decrement value of first operand with given constant value	x= 13 x -= 3 result = 10
*=	Multiply by constant	Multiply the given operand with the constant value	x= 10 x*=3 result = 30
/=	Divide by constant	Divide the operand with given constant value and return the quotient	x = 31 x/=3 result = 10
%=	Remainder by dividing with constant	Divide the operand with given constant value and return the remainder	x= 31 x%=3 result = 1
**	Exponentiation	The result is second operand raised to the power of first operand.	3**2 result = 9

Let’s see the examples for the uses of arithmetic operators:

Addition

Code:

Sum=$((10+3))  
echo "Sum = $Sum"  

Output:

Subtraction

Code:

Difference=$((10-3))  
echo "Difference = $Difference"  

Output:

Multiplication

Code:

Product=$((10*3))  
echo "Product = $Product"  

Output:

Division

Code:

Division=$((10/3))  
echo "Division = $Division"  

Output:

Modulo

Code:

Modulo=$((10%3))  
echo "Modulo = $Modulo"  

Output:

Exponentiation

Code:

Exponent=$((10**2))  
echo "Exponent = $Exponent"  

Output:

Example to show use of all the operators in a single code

Code:

x=10
y=20
echo "x=10, y=5"  
echo "Addition of x and y"  
echo $(( $x + $y ))  
echo "Subtraction of x and y"  
echo $(( $x - $y ))  
echo "Multiplication of x and y"  
echo $(( $x * $y ))  
echo "Division of x by y"  
echo $(( $x / $y ))  
echo "Exponentiation of x,y"  
echo $(( $x ** $y ))  
echo "Modular Division of x,y"  
echo $(( $x % $y ))  
echo "Incrementing x by 10, then x= "  
(( x += 10 ))    
echo $x  
echo "Decrementing x by 15, then x= "  
(( x -= 15 ))  
echo $x  
echo "Multiply of x by 2, then x="  
(( x *= 2 ))  
echo $x  
echo "Dividing x by 5, x= "  
(( x /= 5 ))  
echo $x  
echo "Remainder of Dividing x by 5, x="  
(( x %= 5 ))  
echo $x  

Output:

Different ways to compute Arithmetic Operations in Bash

There are some of the different ways to perform Arithmetic Operations.

1. Double Parenthesis

This could be used for arithmetic expansion. Let’s see an example to see the use of double parenthesis.

Code:

#!/bin/bash
 
first=10
second=3
 
echo $(( first + second ))   # addition
echo $(( $first + $second )) # this is also valid
 
echo $(( first - second ))   # subtraction
echo $(( $first - $second )) # this is also valid
 

 Output:

13
13
7
7

2. Using let command

let command is used to perform arithmetic operations. 

Example

code:

#!/bin/bash
 
x=10
y=3
 
let "z = $(( x * y ))"  # multiplication
echo $z
let z=$((x*y))
echo $z
 
let "z = $(( x / y ))"  # division
echo $z
let z=$((x/y))
echo $z

Output:

30
30
3
3

3. expr command with backticks

Arithmetic expansion could be done using backticks and expr.

Code:

a=10
b=3

# there must be spaces before/after the operator

sum=`expr $a + $b`
echo $sum

sub=`expr $a - $b`
echo $sub

mul=`expr $a \* $b`
echo $mul

div=`expr $a / $b`
echo $div

Output:

13
7
30
3